The NBA Development League, or NBA D-League, is the National Basketball Association's official minor leaguebasketball organization. Known until the summer of 2005 as the National Basketball Development League (NBDL), the NBA D-League started with eight teams in the fall of 2001. In March 2005, NBA commissioner David Stern announced a plan to expand the NBA D-League to fifteen teams and develop it into a true minor leaguefarm system, with each NBA D-League team affiliated with one or more NBA teams. At the conclusion of the 2013–14 NBA season, 33% of NBA players had spent time in the NBA D-League, up from 23% in 2011. Beginning in the 2014–15 season, the league will consist of 18 teams; 17 will be either single-affiliated or owned by an NBA team, with the Fort Wayne Mad Ants being the lone exception.

Today, no NBA D-League teams remain in the league's original Southeastern footprint. On November 5, 2009, the Texas Legends made history by hiring Nancy Lieberman as head coach, the first female head coach to lead an NBA or NBA D-League team.

On January 4, 2010, the league announced its first national television agreement with Versus. Versus is slated to carry 10 regular season games and 6 playoff games throughout 2010, airing on Saturday nights beginning January 16. The league will have a new national broadcast partner in the CBS Sports Network, starting with the 2012–13 season. Select games will also be streamed live on YouTube.

On March 10, 2014, the New York Knicks announced that they had acquired the right to own and operate an NBA D-League team that will play in White Plains, New York starting in the 2014–15 season. The new team will be the NBA D-League’s record 18th team and will be the exclusive affiliate of the New York Knicks, playing its home games at the Westchester County Center, approximately 30 miles north of New York City. With the purchase, the Knicks become the seventh NBA team to fully own and operate their own NBA D-League affiliate.[8] Starting with the 2014-15 season, the league will be divided into two conferences (Eastern and Western) and four divisions (Atlantic, Central, Southwest, and West).[9][10]

The NBA D-League Draft occurs each season and is the major source from which teams build their rosters. Team rosters are made up of returning players (players who were on the team during the previous season), allocated players (players who have local significance), and drafted players. The 8 round draft utilizes a "serpentine" format, meaning the order alternates in each round; Team A who selected first in Round 1 will select last in Round 2, while Team B who selected last in Round 1 will get the first pick in Round 2. Round 3 was added in 2014

Players for NBA D-League teams do not sign contracts with the individual teams, but with the league itself. D-League team rosters consist of a total of 12 players, 10 (or fewer) being D-League players and two (or more) NBA players. The rosters are made up in a number of ways: the previous years' players, players taken in the D-League draft, allocation players (meaning players who are assigned to a team with which they have a local connection, such as a University of Texas player being assigned to the Austin Toros), NBA team assignments, and local tryouts.

Each NBA team can assign two first- or second-year players to its affiliated D-League team. If more than two NBA players are assigned to a team, the team must reduce the number of D-League players to keep the total roster size to 12. An NBA player will continue to be paid his NBA salary and will continue to be included on his NBA team’s roster on the inactive list while playing in the D-League.[17] Each team also has local tryouts, and one player from the tryouts is assigned to the team.

The minimum age to play in the NBDL is 18,[18] unlike the NBA which requires players to be 19 years old and one year out of high school in order to sign an NBA contract or be eligible for the draft. The tallest player ever to be assigned is Hasheem Thabeet, the second player selected in the 2009 NBA Draft.

NBA teams can call up players as many times as they choose, and there is no limit to the number of times an NBA player with three years or less experience can be assigned to the D-League. Starting in 2011–12, veteran NBA players could be assigned with their consent.[19] The first example of such was with Yi Jianlian, who the Dallas Mavericks assigned to the Texas Legends for two games.

Ownership models vary across the NBA D-League. Independent owners control most of the league’s teams, but growing willingness among NBA organizations to invest in the D-League has led to two other models: direct ownership of D-League teams by parent NBA clubs and single-affiliate partnerships in which the D-League team remains independently owned while the parent club runs and finances basketball operations.

D-League teams with either hybrid or direct ownership by their mother NBA clubs also adopt the colors and motifs used by the latter; exceptions include the Celtics and Red Claws, the Magic and Bayhawks, the Suns and Jam, the Jazz and Stampede, and the Kings and Bighorns.

^"CBA Principal Deal Points". NBA. August 4, 2005. Retrieved January 19, 2011. The player will continue to be paid his NBA salary and will continue to be included on his NBA team’s roster (on the inactive list) while playing in the NBADL.